The present invention relates generally to increasing the spectral efficiency of communications channels limited by bandwidth restrictions. The method of the invention addresses increasing the bandwidth efficiency of any method of communications, whether wired, fiber, cable, wireless, optical, IR or RF communications, and at any signal frequency or for any channel bandwidth. The methods of prior art have not addressed increasing efficiency by overlaying signals in ways that are empirically realizable, nor by overlaying signals in time and frequency, nor by the specific methods described here. The invention increases spectral efficiency by increasing the effective bandwidth without increasing the physical bandwidth.
The methods described here permit the spectral overlay of signals within a transmitted symbol, each signal constituting a separate communications channel that can be modulated for data encoding by well-known methods, e.g., quadrature amplitude modulation (QAM), but yet without the need for additional physical bandwidth. Each signal overlaid within a symbol is orthogonal, and not because of spectral or time displacement, but because of minimum cross-correlation (or minimum least squares) when overlaid. As this new multiplexing method requires overlaid orthogonal signals to constitute the symbol, the method is called “Orthogonal Signal Spectrum Overlay” (OSSO).